Approach to take on adding a new report destination option in AX 365?

Can anyone give me a general idea on  how to add a new report destination option in AX 365?

I took a look into the standard report printer code and realized that I will need to modify the SRSReportRunPrinter and some other related classes to implement the new print destination option.  However I found the objects belong to Application foundation package can’t be customized, and I am not sure if it can be accomplished by extension method.   

To rephrase , I can extend the SRSReportRunPrinter class to add a new method  for the Web service option, but I will still have to customize the SrsReportRunService class to call the new extension method. However the SrsReportRunService class belongs to Application foundation package, it can’t be customized. What to do here?

Thanks in advance.